Summary
Objectives: to evaluate in vitro the strength of different compositions of beta-tricalcium phosphate (β-TCP) wedges
in comparison with titanium foam and cages. To study the response to cyclic loading
of the strongest β-TCP wedge, titanium foam and titanium cage.
Methods: Compression test: Twenty-five tibiae were prepared for tibial tuberosity advancement using the modified
Maquet technique. Five groups were defined depending on the material used to maintain
the tibial tuberosity: Group 1 = titanium cage; Group 2 = wedges of porous titanium
foam with 50% porosity (OrthoFoam®); Group 3 = blocks of biphasic synthetic bone (60%
hydroxyapatite [HAP] and 40% _-TCP, porosity 80%); Group 4 = blocks of biphasic synthetic
bone (60% HAP and 40% _-TCP, porosity 70%) and Group 5 = blocks of biphasic synthetic
bone (65% HAP and 35% _-TCP, porosity 60%). Loads to failure were calculated for each
implant. Cyclic study: Five additional tibiaes of group 1, 2 and 5 were fatigue tested
from 100 to 500 N at a rate of 4 Hz for 200,000 cycles or until failure.
Results: Compression test: For the five groups, the mean load at failure was 1895 N, 1917 N, 178 N, 562 N and
1370 N respectively. Cyclical study: All samples in the three groups tested withstood 200,000 cycles without failure.
Clinical significance: The ideal implant to maintain tibial tuberosity advancement after the modified Maquet
technique would be absorbable and allow osteoconduction and osteoinduction. As such,
β-TCP wedges have many advantages and our study shows that they can withstand loads
in the patellar tendon up to 500 N over 200,000 cycles in vitro and deserve more investigation.
Keywords
Beta-tricalcium phosphate - modified Maquet technique - cruciate - ligament - dog
